1. Field of the Invention
The present invention relates to a film forming method and a film forming apparatus each for supplying a processing solution to a substrate to form a film of the processing solution.
2. Description of the Related Art
A lithography process in semiconductor device fabrication, for example, has various processing steps such as a resist coating processing step of applying a resist solution to the front surface of a semiconductor wafer (hereinafter referred to as xe2x80x9ca waferxe2x80x9d) or the like, an exposure processing step of exposing the wafer after resist coating processing, a developing processing step of developing the wafer after exposure processing, and the like. A spin coating method is adopted, for example, in the resist coating processing step.
In this spin coating method, a predetermined amount of resist solution is dropped to a central portion of the wafer, the wafer is then rotated, and thus the resist solution at the central portion is spread over the wafer by centrifugal force to form a resist film.
Incidentally, it is required to form a uniform resist film on the front surface of the wafer for improving yield of products. Therefore, in the conventional spin coating method, the wafer is rotated at a high speed, and thus the resist solution is spread by centrifugal force, which allows the resist solution to fully spread to a peripheral portion of the wafer.
When the wafer is rotated at a high speed as described above, however, the resist solution scattered from the front surface of the wafer increases in amount, thus causing waste. If the wafer is rotated at a low speed in order to prevent the above waste, the applied resist solution can not fully spread to the peripheral portion of the wafer, and consequently a uniform resist film can not be formed.
An object of the present invention is to provide a film forming method and a film forming apparatus capable of decreasing the amount of processing solution by eliminating the aforesaid waste and forming a uniform processing solution film on a substrate.
To attain the above object, a first aspect of the present invention is a method for forming a film of a processing solution on a substrate, comprising the steps of rotating the substrate, supplying the processing solution discharged from a nozzle onto the rotating substrate, moving a position on the substrate of the processing solution to be supplied from the nozzle nearly in a radial direction of the rotating substrate, and performing control such that the processing solution to be supplied onto the substrate is uniform.
According to the present invention, if the processing solution is discharged to the rotating substrate from the nozzle which moves at a constant speed along the radial direction of the substrate, for example, the processing solution is supplied to the substrate drawing a spiral track. In this situation, if the supply amount of the processing solution is gradually decreased from a peripheral portion of the substrate to a central portion of the substrate, for example, the processing solution can be supplied uniformly onto the substrate. Consequently, it becomes unnecessary to spread the processing solution by centrifugal force, a uniform processing solution film can be formed even if the wafer is rotated at a low speed, and scattering of the processing solution from the substrate can be prevented.
These objects and still other objects and advantages of the present invention will become apparent upon reading the following specification when taken in conjunction with the accompanying drawings.